The present invention relates to new camptothecin analogue compounds.
Camptothecin, an alkaloid isolated from Camptotheca accuminata, is an anti-cancer agent having a broad spectrum of activity. Its insoluble nature has for a long time directed research towards the insoluble salts of the compound, the toxicity of which has proved to be a major handicap. Several other studies have been carried out with a view to obtaining structural analogues and to overcoming the lack of solubility of the natural molecule (J. Med. Chem., 1991, 34, 98; Chem. Pharm. Bull., 1991, 39, 3183). The modifications made relate principally to the A and B rings. The conclusions of different studies also show the importance of the E ring and more especially of the lactone function. In fact, the latter, in equilibrium with the open hydroxy-acid form, appears to be the most active form having reduced undesirable effects (Cancer Res., 1989, 49, 1465; ibid, 1989, 49, 5077). Attempts at modifying this ring have been carried out, in particular the cyclic oxygen atom has been replaced by a nitrogen or sulphur atom, but in each case there is a loss of pharmacological activity, so confirming the importance of the lactone (J. Med. Chem., 1989, 32, 715).
The present invention relates to camptothecin structural analogue compounds, the E ring of which has been modified. They are characterised by the replacement of the lactone function of that ring by a cyclic ketone function, the cyclic oxygen having been replaced by a carbon atom. The compounds so obtained have a novel structure and, surprisingly, have a significant cytotoxic character. It will therefore be possible to use them in the manufacture of medicaments for use in the treatment of cancerous diseases.
The invention relates to the compounds of formula (I): 
wherein:
n is 0, 1 or 2,
R1 represents (C3-C11)cycloalkyl or (C3-C11)cycloalkylalkyl,
R2, R3, R4 and R5 are selected each independently of the others from a hydrogen atom, a halogen atom, an alkyl group, an alkenyl group, an alkynyl group, a perhaloalkyl group, a (C3-C11)cycloalkyl group, a (C3-C11)cycloalkyl-alkyl group, a hydroxy group, a hydroxyalkyl group, an alkoxy group, an alkoxyalkyl group, an alkoxycarbonyl group, an acyloxy group, a carboxy group, a nitro group, a cyano group, an aminocarbonyl group (optionally substituted on the nitrogen atom by one or two alkyl groups), and the groups (CH2)pxe2x80x94NRaRb and xe2x80x94Oxe2x80x94C(O)xe2x80x94Nxe2x80x94RaRb, wherein p is an integer from 0 to 6, and Ra and Rb each independently of the other represents a hydrogen atom, an alkyl group, a (C3-C11)cycloalkyl group, a (C3-C11)cycloalkyl-alkyl group, an acyl group, an optionally substituted aryl group or an optionally substituted arylalkyl group, or Ra and Rb form together with the nitrogen atom carrying them a pyrrolyl, piperidinyl or piperazinyl group, it being possible for each of those cyclic groups to be optionally substituted, or two adjacent groups R2, R3, R4 and R5 form together with the carbon atoms carrying them a group xe2x80x94Oxe2x80x94(CH2)txe2x80x94O, t being an integer from 1 to 3 inclusive,
R60, R70n, R80 and R90 each independently of the others represents a hydrogen atom, a hydroxy group, an alkoxy group, or a group Oxe2x80x94(CO)xe2x80x94X or Oxe2x80x94(CO)xe2x80x94NXW wherein X and W each independently of the other represents an alkyl group, an alkenyl group, an alkynyl group, a (C3-C11)cycloalkyl group, a (C3-C11)cycloalkyl-alkyl group, an optionally substituted aryl group or an optionally substituted arylalkyl group,
R61, R71n, R81 and R91 each independently of the others represents a hydrogen atom, an alkyl group, an alkenyl group or an alkynyl group, or, taken in pairs on adjacent carbon atoms, together form a bond or an oxirane group, or two geminal groups (R60 and R61) and/or (R70n and R71n) and/or (R80 and R81) and/or (R90 and R91) together form an oxo group or a group xe2x80x94Oxe2x80x94(CH2)t1xe2x80x94O, t1 being an integer from 1 to 3 inclusive,
with the proviso that R60, R61, R70n, R71n, R80, R81, R90 and R91 do not all represent a hydrogen atom,
their enantiomers, diastereoisomers, and addition salts thereof with a pharmaceutically acceptable acid or base,
it being understood that
the term xe2x80x9calkylxe2x80x9d denotes a linear or branched chain having from 1 to 6 carbon atoms,
the term xe2x80x9calkenylxe2x80x9d denotes a linear or branched chain having from 2 to 6 carbon atoms and containing from 1 to 3 double bonds,
the term xe2x80x9calkynylxe2x80x9d denotes a linear or branched chain having from 2 to 6 carbon atoms and containing from 1 to 3 triple bonds,
the term xe2x80x9calkoxyxe2x80x9d denotes a linear or branched alkyl-oxy radical containing from 1 to 6 carbon atoms,
the term xe2x80x9cacylxe2x80x9d denotes a linear or branched alkyl-carbonyl radical containing from 1 to 6 carbon atoms,
the term xe2x80x9carylxe2x80x9d represents a phenyl or naphthyl group,
the expression xe2x80x9csubstitutedxe2x80x9d when used in relation to aryl or arylalkyl groups means that the groups in question are substituted by one or more halogen atoms, and/or groups alkyl, alkoxy, hydroxy, cyano, nitro, and/or amino (optionally substituted by one or two alkyl groups),
the expression xe2x80x9csubstitutedxe2x80x9d when used in relation to pyrrolyl, piperidinyl or piperazinyl groups means that the groups in question are substituted by one or more alkyl, alkoxy, aryl, arylalkyl, aryloxy and/or aryloxyalkyl groups.
An advantageous aspect of the invention relates to compounds of formula (I) wherein R60 represents a hydroxy group and R61 represents an alkyl group (for example ethyl).
Another advantageous aspect of the invention relates to compounds of formula (I) wherein R80 and R81 together form an oxo group, or R90 and R91 together form an oxo group, or R80 with R81 and R90 with R91 form two oxo groups.
Preferred compounds of formula (I) are those wherein R1 represents a hydrogen atom.
Other preferred compounds of formula (I) are those wherein R2, R3, R4 and R5 are selected from a hydrogen atom, a halogen atom, an alkyl group and an alkoxy group, or two of those groups, when bonded to two adjacent carbon atoms, together form a methylenedioxy or ethylenedioxy group (preferably methylenedioxy). Among those compounds, preference is given to those wherein each of R2 and R5 represents a hydrogen atom.
An especially advantageous aspect of the invention relates to compounds of formula (I) wherein each of R2 and R5 represents a hydrogen atom, R3 and R4 are selected from a hydrogen atom, a halogen atom, an alkyl group and an alkoxy group, or together form a methylenedioxy group, R60, R70, R80 and R90 each independently of the others represents a hydrogen atom, a hydroxy group or an alkoxy group, and R61, R71, R81 and R91 each independently of the others represents a hydrogen atom or an alkyl group, or, taken in pairs on adjacent carbon atoms, together form a bond or an oxirane group, or two geminal groups (R60 and R61) and/or (R70n and R71) and/or (R80 and R81) and/or (R90 and R91) together form an oxo group.
The present invention relates also to a process for the preparation of compounds of formula (I), characterised in that there is used as starting material a compound of formula (II):
The present invention relates also to a process for the preparation of compounds of formula (I), characterised in that there is used as starting material a compound of formula (II): 
wherein n, R60, R61, R70n, R71n, R80, R81, R90 and R91 are as defined for formula (I),
which is condensed, in a basic medium, with a compound of formula (III): 
wherein R1, R2, R3, R4 and R5 are as defined for formula (I), and Hal and Halxe2x80x2 each independently of the other represents a halogen atom,
or, in accordance with the conditions of a Mitsunobu reaction, with a compound of formula (IIIxe2x80x2): 
wherein R1, R2, R3, R4, R5 and Hal are as defined hereinbefore,
to yield a compound of formula (IV): 
wherein R1, R2, R3, R4, R5, n, R60, R61, R70n, R71n, R80, R81, R90, R91 and Hal are as defined hereinbefore,
which compound (IV) is subjected to an intramolecular cyclisation reaction of the xe2x80x9cHeckxe2x80x9d type catalysed by a palladium compound, to yield a compound of formula (I),
it being understood, for the purpose of simplifying the above process, that the reactive groups present in R60, R61, R70n, R71n, R80, R81, R90 and R91 can be protected by conventional protecting groups and deprotected at the appropriate time point, that the hydroxy groups present in those same positions can be oxidised by conventional chemistry methods to oxo groups, and, conversely, the oxo groups present in those same positions can be reduced by conventional reducing agents at any appropriate time point in the synthesis, and that, when two of those groups together form a bond, the latter can be introduced at any time point deemed suitable by the person skilled in the art in order to facilitate the synthesis,
which compounds of formula (I):
can be purified, if necessary, according to a conventional purification technique,
are separated, where appropriate, into their stereoisomers according to a conventional separation technique,
are converted, if desired, into addition salts thereof with a pharmaceutically acceptable acid or base.
The substrates of formulae (II) and (III) are commercial products or are prepared according to known procedures or using conventional reactions of organic chemistry. By way of illustration, there may be mentioned the processes described in J. Am. Chem. Soc., 1992, 37, 10971.
In particular, it is possible to prepare a substrate of formula (IIxe2x80x2): 
wherein n, R60, R61, R70n, R71n, R80, R81, R90 and R91 are as defined for formula (I) and * indicates that the carbon atom carrying the groups R60 and R61 has a fixed configuration (R) or (S),
in order to obtain, according to the process described hereinbefore, a compound of formula (Ixe2x80x2): 
wherein R1, R2, R3, R4, R5, n, R60, R61, R70n, R71n, R80, R81, R90 and R91 are as defined for formula (I) and * indicates that the configuration of the carbon atom is fixed.
Among the pharmaceutical compositions according to the invention, there may be mentioned more especially those that are suitable for oral, parenteral or nasal administration, tablets or dragees, sublingual tablets, gelatin capsules, lozenges, suppositories, creams, ointments, dermal gels, etc.
The useful dosage varies according to the age and weight of the patient, the nature and severity of the disorder and the route of administration, which may be oral, nasal, rectal or parenteral. The unit dose generally ranges from 0.1 to 500 mg for a treatment in from 1 to 3 administrations per 24 hours.
The following Examples illustrate the invention but do not limit it in any way.
The starting materials used are known products or are prepared according to known procedures.
The structures of the compounds described in the Examples and the Preparations were determined according to the usual spectrophotometric techniques (infrared, NMR, mass spectrometry, etc.).
Preparation A: 7-Hydroxy-6,7-dihydro-1H-cyclopenta[c]pyridine-1,5(2H)-dione
Step 1: 4-(1-Ethoxyvinyl)-2-fluoro-3-pyridinecarbaldehyde
There are mixed in succession 8 g (31.9 mmol) of 2-fluoro-4-iodo-3-pyridinecarbaldehyde (described in J.O.C, 1993, 58, pp. 7832), 12.7 g (35.96 mmol) of 1-ethoxyvinyltributyltin and 740 mg of tetrakis(triphenylphosphine)palladium (2% molar) in 280 ml of dioxane. The reaction mixture is heated at reflux until the starting material has disappeared completely. After returning to room temperature a solution of potassium fluoride is added to the reaction mixture. Vigorous stirring is maintained for 10 minutes in order to cause precipitation of the tributyltin fluoride, which is filtered off. The filtrate is plunged into a sodium chloride solution. The aqueous phase is extracted 3 times with dichloromethane and then the organic phases are combined, dried over magnesium sulphate, concentrated and purified by chromatography over a silica column, using a dichloromethane/cyclohexane mixture (95/5) as eluant to yield the expected product.
Step 2: 7-Hydroxy-6,7-dihydro-1H-cyclopenta[c]pyridine-1,5(2H)-dione
A mixture of 770 g (3.93 mmol) of the compound described in the preceding Step in 51 ml (102.1 mmol) of 2N hydrochloric acid is refluxed with air cooling for 2 hours, cooled and then concentrated. The resulting residue is washed in acetone, filtered and then recrystallised from isopropanol to yield the expected product.
Melting point: 200xc2x0 C. (isopropanol)
Preparation B: 5-Ethyl-5,7-dihydroxy-2,5,6,7-tetrahydro-1H-cyclopenta[c]-pyridin-1-one
Step 1: 1-Fluoro-7-hydroxy-6,7-dihydro-5H-cyclopenta[c]pyridin-5-one
The process used is identical to that described in Preparation A, Step 1, using a dichloromethane/methanol mixture as eluant in the course of the purification. The resulting residue is stirred at room temperature for 3 hours in a solution of 16 ml of trifluoroacetic acid, 90 ml of acetonitrile and 35 ml of water. The reaction mixture is then neutralised with an aqueous K2CO3 solution and extracted 3 times with dichloromethane. The combined organic phases are dried over magnesium sulphate, filtered, concentrated and purified by chromatography over a silica column (eluant: dichloromethane/methanol 99.5/0.5) to obtain the expected compound.
Step 2: 5,7-Dihydroxy-5-ethyl-1-fluoro-6-6,7-dihydro-1H-cyclopenta[c]pyridine
At xe2x88x9230xc2x0 C., 1.6 ml (4.7 mmol) of a solution of 3M ethylmagnesium bromide in ether are added dropwise to a solution of 350 mg (2.1 mmol) of the compound described in the preceding Step in 60 ml of ether. The reaction mixture is stirred at xe2x88x9230xc2x0 C. for 3 hours before being hydrolysed with a saturated ammonium chloride solution. The organic phase is decanted, the aqueous phase is extracted 3 times with ethyl acetate and then the combined organic phases are dried over magnesium sulphate and filtered, concentrated, and purified by chromatography over a silica column (eluant: dichloromethane/acetone, 95/5) to yield the expected product.
Step 3: 5-Ethyl-5,7-dihydroxy-2,5,6,7-tetrahydro-1H-cyclopenta[c]pyridin-1-one
The expected product is obtained according to the process described in Step 2 of Preparation A using the compound described in the preceding Step as starting material.
Preparation C: 5-Ethyl-5,6-dihydroxy-2,5-dihydro-1H-cyclopenta[c]pyridin-1-one
0.5 g of sodium borohydride (13.20 mmol) is added at room temperature to a solution of 2 g of the product described in Preparation F (9.65 mmol) in 20 ml of methanol. After stirring for 30 minutes at room temperature, 20 ml of an aqueous saturated sodium hydrogen carbonate solution are added. The mixture is extracted with ethyl acetate. The organic phases are dried over magnesium sulphate, filtered and concentrated in vacuo to obtain the expected compound.
Preparation D: 5-Ethyl-5-methoxymethoxy-2H,5H-[2]pyridine-1,6,7-trione
A solution of 2.35 g (21.2 mmol) of selenium oxide in 3 ml of water is added to a solution of 3 g (10.6 mmol) of the compound prepared in Step 3 of Preparation F in 130 ml of dioxane. The reaction mixture is heated at 60xc2x0 C. for 48 hours. The reaction mixture is filtered, the filtrate is concentrated in vacuo and the residue is taken up in ethyl acetate. The expected product is obtained by filtering off the precipitate.
Preparation E: 5-Ethyl-5-hydroxy-5,6-dihydro-1H-cyclopenta[c]pyridine-1,7-(2H)-dione
Step 1: 5-Ethyl-1-fluoro-5-hydroxy-1,2,5,6-tetrahydro-7H-cyclopenta[c]pyridin-7-one
3 g of Celite, 4 xc3x85 molecular sieve, and then, in small fractions, 3.6 g (16.7 mmol) of pyridinium chlorochromate are added, in succession, to a solution, stirred at 0xc2x0 C., of 3 g (15.2 mmol) of the compound described in Step 2 of Preparation B in a mixture of dichloromethane/acetone (15/1 v/v). The reaction mixture is stirred at room temperature for 20 hours and filtered, the solid is washed 3 times with 50 ml of a dichloromethane/acetone mixture (50/50 v/v) each time, and the filtrate is concentrated in vacuo. The resulting residue is purified by chromatography over silica (eluant: dichloromethane/acetone 85/15) to yield the expected product.
Step 2: 5-Ethyl-5-hydroxy-5,6-dihydro-1H-cyclopenta[c]pyridine-1,7(2H)-dione
A suspension of 3.5 g (17.7 mmol) of the compound described in the preceding Step in 360 ml of 1N hydrochloric acid is heated at 80xc2x0 C. for 1 hour. The reaction mixture is concentrated in vacuo. The solid residue is stirred in ether, and the precipitate is filtered off and dried to yield the expected product.
Preparation F: 5-Ethyl-6-[2-(1,3-dioxolan)yl]-5-hydroxy-5,7-dihydro-1H-cyclopenta[c]pyridin-1(2H)-one
Step 1: Methyl 2-(2-fluoro-3-methyl-4-pyridinyl)-2-hydroxybutanoate
6.9 ml (11 mmol) of 1.6M butyllithium in hexane are added dropwise to a solution, stirred at xe2x88x9278xc2x0 C. of 2.6 g (11 mmol) of 2-fluoro-4-iodo-3-methylpyridine (described in J.O.C., 1993, 58, pp. 7832) in 100 ml of THF. The reaction mixture is then stirred for 10 minutes at xe2x88x9278xc2x0 C. before the addition of a solution of 1.5 g (12.9 mmol) of methyl 2-oxo-butyrate in 20 ml of THF. The reaction mixture is stirred for 10 minutes at xe2x88x9278xc2x0 C., and then hydrolysed with a mixture of water/THF. The aqueous phase is decanted and then extracted 3 times with 50 ml of methyl acetate each time. The combined organic phases are dried, concentrated and purified by chromatography over silica (eluant dichloromethane/acetone 95/5) to yield the expected product.
Step 2: Methyl 2-(2-fluoro-3-methyl-4-pyridinyl)-2-methoxymethoxylbutanoate
260 mg (8.8 mmol) of an 80% suspension of sodium hydride in mineral oil are added in small fractions to a solution, stirred at 0xc2x0 C., of 2 g (8.8 mmol) of the compound described in the preceding Step in 60 ml of THF. Once the addition is complete, the mixture is stirred at room temperature until the evolution of gas has ceased. A solution of 0.94 g (11.6 mmol) of chloromethyl methyl ether in 10 ml of THF is then added dropwise and the mixture is stirred at room temperature for 2 hours, hydrolysed with 2N hydrochloric acid and decanted. The aqueous phase is extracted with dichloromethane, and the combined organic phases are dried over magnesium sulphate and concentrated. The expected product is obtained by chromatography of the residue over silica (eluant: dichloromethane/acetone 95/5).
Step 3: 5-Ethyl-1-fluoro-5-(methoxymethoxy)-5,7-dihydro-6H-cyclopenta[c]-pyridin-6-one
55 ml (88.5 mmol) of a 1.6M butyllithium solution in hexane are added to a solution, stirred at 0xc2x0 C., of 9 g (88.5 mmol) of diisopropylamine in 160 ml of THF. The mixture is stirred for xc2xd hour at 0xc2x0 C. before the dropwise addition, at that temperature, of 15.8 g (88.5 mmol) of hexamethylphosphoramide. The mixture is again stirred at 0xc2x0 C. for xc2xd hour before the dropwise addition of a solution of 5.3 g (19.5 mmol) of the compound described in the preceding Step in 40 ml of THF. The reaction mixture is stirred for 1 hour at room temperature before being hydrolysed with water. The aqueous phase is extracted with ethyl acetate, and the organic phase is washed with a 2N hydrochloric acid solution and then with a saturated sodium chloride solution, dried over magnesium sulphate and concentrated. The resulting residue is purified by chromatography over silica (eluant dichloromethane/acetone 95/5) to yield the expected product.
Step 4: 5-Ethyl-5-hydroxy-5,7-dihydro-1H-cyclopenta[c]pyridine-1,6(2H)-dione
A suspension of 1 g (4.18 mmol) of the compound described in the preceding Step in 40 ml of 3N hydrochloric acid is refluxed for 1 hour. The mixture is concentrated, the resulting residue is taken up in ether and decanted and, after the addition of acetonitrile, the resulting solid is filtered off and washed with ether to yield the expected product.
Step 5: 5-Ethyl-6-[2-(1,3-dioxolan)yl]-5-hydroxy-5,7-dihydro-1H-cyclopenta[c]-pyridin-1
A suspension of 2.5 g (13 mmol) of the compound prepared in the preceding Step, 15 ml of ethylene glycol and 40 mg of para-toluenesulphonic acid in 40 ml of toluene is refluxed for 4 hours. The mixture is concentrated in vacuo, the black residue is taken up in ethyl acetate, and the resulting white precipitate is filtered off to yield the expected product.
Preparation G: 5-Ethyl-5-hydroxy-7,8-dihydro-1,6(2H, 5H)-isoquinolinedione
Step 1: 3-(1,3-Dioxolan-2-yl)-2-fluoro-4-iodopyridine
In a three-necked flask equipped with a Dean Stark apparatus, a mixture of 5.1 g (20.3 mmol) of 2-fluoro-4-iodo-3-pyridinecarbaldehyde, 1.4 g (22.3 mmol) of ethane-1,2-diol, and 50 mg of para-toluenesulphonic acid in 100 ml of toluene is heated at reflux. When the theoretical amount of water has been collected, the reaction mixture is cooled to room temperature, washed with a saturated sodium hydrogen carbonate solution and dried over magnesium sulphate. The expected product is obtained by concentration.
Step 2: Methyl 2-[3-(1,3-dioxolan-2-yl)-2-fluoro-4-pyridinyl]-2-hydroxybutanoate
6.9 ml (11 mmol) of 1.6M butyllithium in hexane are added dropwise to a solution, stirred at xe2x88x9278xc2x0 C. under an argon atmosphere, of 3.1 g (11 mmol) of 3-(1,3-dioxolan-2-yl)-2-fluoro-4-iodopyridine in 100 ml of THF. The reaction mixture is then stirred for 10 minutes at xe2x88x9278xc2x0 C. before the dropwise addition of a solution of 1.5 g (13 mmol) of methyl 2-oxo-butyrate in 20 ml of THF. The mixture is stirred for 3 hours at xe2x88x9278xc2x0 C., hydrolysed with a mixture of water/THF, and decanted. The aqueous phase is extracted 3 times with 50 ml of ethyl acetate each time, and the combined organic phases are dried over magnesium sulphate and then concentrated. The expected product is obtained by purification of the residue by chromatography over silica (eluant: dichloromethane/acetone 95/5).
Step 3: Methyl 2-(benzyloxy)-2-[3-(1,3-dioxolan-2-yl)-2-fluoro-4-pyridinyl]-butanoate
A solution of 14.8 g (51.8 mmol) of the compound described in the preceding Step in 100 ml of DMF is added dropwise to a suspension, stirred at 0xc2x0 C., of 2 g (67.4 mmol) of 80% sodium hydride in 100 ml of DMF. Once the addition is complete, the mixture is stirred for xc2xd hour before the addition, at that temperature, in succession, of 0.15 g of tetrabutylammonium iodide, and then 9.8 g (57.1 mmol) of benzyl bromide dissolved in 50 ml of DMF. The mixture is stirred for 2 hours at 0xc2x0 C., plunged into ice-cold water and extracted with ethyl acetate, and the organic phase is washed with water and then dried over magnesium sulphate and concentrated. The expected product is obtained by purification of the residue over silica gel (eluant: dichloromethane/acetone 95/5).
Step 4: Methyl 2-(benzyloxy)-2-[3-(dimethoxymethyl)-2-fluoro-4-pyridinyl]-butanoate
A solution of 3.4 g (9 mmol) of the ester described in the preceding Step and 0.1 g of para-toluenesulphonic acid in 250 ml of methanol is stirred at room temperature for 24 hours. The solvent is concentrated. The crude residue is taken up in ethyl acetate, and the organic phase is neutralised with a saturated sodium hydrogen carbonate solution, washed with water and dried over magnesium sulphate. The expected product is obtained by concentration.
Step 5: Methyl 2-(benzyloxy)-2-(2-fluoro-3-formyl-4-pyridinyl)butanoate
A solution of 20.3 g (0.178 mmol) of trifluoroacetic acid in 20 ml of water is added to a solution of 3.3 g (8.75 mmol) of the ester described in the preceding Step in 60 ml of dichloromethane. The reaction mixture is stirred for 18 hours at room temperature and decanted. The aqueous phase is extracted with dichloromethane, and the combined organic phases are washed with a sodium hydrogen carbonate solution and then with salt water, and dried over magnesium sulphate. The expected product is obtained by concentration.
Step 6: Methyl 3-{4-[1-(benzyloxy)-1-(methoxycarbonyl)propyl]-2-fluoro-3-pyridinyl}-2-acrylate
A mixture of 21 g (63.3 mmol) of the product described in the preceding Step and 22.3 g (63.3 mmol) of carboxymethylenetriphenylphosphorane in 1 litre of toluene is heated at reflux for 2 hours 30 minutes. After returning to room temperature, the solvent is removed by evaporation, the residue is crystallised from ether, the crystals are filtered off and the filtrate is concentrated in cacao. The residue is purified by chromatography over silica gel (eluant: dichloromethane/acetone, from 100/0 to 96/4) to yield the expected product.
Step 7: Methyl 2-(benzyloxy)-2-{2-fluoro-3-[2-(methoxycarbonyl)ethyl]-4-pyridinyl}butanoate
2.5 g (10.5 mmol) of cobalt chloride are added to a solution, stirred at 0xc2x0 C., of 16.3 g (42 mmol) of the compound described in the preceding Step in 900 ml of methanol. The reaction mixture is stirred at 0xc2x0 C. for 10 minutes, and then 3.2 g (84 mmol) of sodium borohydride are added in small fractions. The mixture is then concentrated in vacuo, the residue is taken up in ethyl acetate, and the organic phase is washed with water, dried over magnesium sulphate, filtered over Celite and concentrated to yield the expected product.
Step 8: Methyl 2-(benzyloxy)-2-[3-(3-methoxy-3-oxopropyl)-2-oxo-1,2-dihydro-4-pyridinyl]butanoate
257 ml of a Normal solution of hydrochloric acid are added to a solution of 5 g (12.83 mmol) of the compound described in the preceding Step in 80 ml of dioxane. The reaction mixture is then refluxed for 1 hour 30 minutes. After returning to room temperature, the mixture is concentrated in vacuo, and the residue is purified by chromatography over silica gel (eluant: dichloromethane 97/methanol 3) to yield the expected product.
Step 9: Methyl 5-(benzyloxy)-5-ethyl-6-hydroxy-1-oxo-1,2,5,8-tetrahydro-7-isoquinolinecarboxylate
200 ml of a solution of 4.7 g (12.1 mmol) of the compound described in the preceding Step in THF are added dropwise to a suspension, stirred at 0xc2x0 C., of 0.8 g (26.7 mmol) of 80% sodium hydride in 50 ml of THF. The mixture is then stirred for 15 minutes at 0xc2x0 C., for 15 minutes at room temperature and then for 1 hour at reflux before being hydrolysed at 0xc2x0 C. with a Normal solution of hydrochloric acid until the pH is neutral. The aqueous phase is extracted with dichloromethane. The organic phase is washed with water, dried over magnesium sulphate and concentrated to yield the expected product.
Step 10: 5-(Benzyloxy)-5-ethyl-7,8-dihydro-1,6(2H, 5H)-isoquinolinedione
A suspension of 16.1 g (45.3 mmol) of the compound described in the preceding Step in 60 ml of a Normal solution of potassium hydroxide is heated at reflux for 30 minutes. The reaction mixture is neutralised at 0xc2x0 C. by the dropwise addition of a 2N solution of hydrochloric acid and then extracted with dichloromethane. The organic phase is filtered, dried over magnesium sulphate and concentrated. The expected product is obtained after purification by chromatography over silica gel (eluant: dichloromethane/methanol from 100/0 to 96/4).
Step 11: 5-Ethyl-5-hydroxy-7,8-dihydro-1,6(2H,5H)-isoquinolinedione
A solution of 7.9 g (26.56 mmol) of the compound described in the preceding Step in 800 ml of methanol is stirred at atmospheric pressure and room temperature under a hydrogen atmosphere in the presence of 0.8 g of 10% palladium-on-carbon. After absorption of the theoretical amount of hydrogen (approximately 3 hours 30 minutes), the catalyst is removed by filtration, the filtrate is concentrated, and the expected product is obtained by cristallisation of the residue from ether.
Preparation H: 5-Ethyl-5-hydroxy-7-methoxy-2,5,6,7-tetrahydro-1H-cyclopenta[c]pyridin-1-one
A suspension of 2.2 g (11.95 mmol) of the compound described in Step 2 of Preparation B in 220 ml of IN hydrochloric acid is heated at 80xc2x0 C. for 1 hour 30 minutes. The reaction mixture is concentrated, and the residue is purified by chromatography over silica gel (eluant: dichloromethane/methanol 95/5) to yield the expected compound.
Preparation I: (5S)-5-Ethyl-5-hydroxy-5,7-1H-cyclopenta[c]pyridine-1,6-(2H)-dione
Step 1: 3-(3-Allyl-2-fluoro-4-pyridinyl)-3-pentanol
27 ml (43.3 mmol) of 1.6M butyllithium in hexane are added, at xe2x88x9275xc2x0 C., to a solution of 11.4 g (43.3 mmol) of 3-allyl-2-fluoro-4-iodopyridine (prepared according to the process described in J.O.C., 1993, 58, pp. 7832) in 250 ml of THF. After 30 minutes"" stirring at xe2x88x9275xc2x0 C., a solution of 4.6 ml of 3-pentanone in 100 ml of THF is added dropwise. The reaction mixture is stirred for 6 hours at xe2x88x9275xc2x0 C. After returning to room temperature, the mixture is hydrolysed with 100 ml of water and extracted with ethyl acetate. The organic phase is dried, concentrated and purified by chromatography over silica (eluant: cyclohexane/ethyl acetate 8/2) to yield the expected product.
Step 2: 3-Allyl-4-(1-ethyl-1-propenyl)-2-fluoropyridine
17.6 ml (126 mmol) of triethylamine are added to a solution of 1.4 g (6.3 mmol) of the compound described in the preceding Step in 50 ml of dichloromethane. The temperature is reduced to 0xc2x0 C. and 2.3 ml (31.5 mmol) of thionyl chloride in 20 ml of dichloromethane are added. After 5 minutes"" stirring at room temperature, the reaction mixture is poured into 70 ml of water and then extracted with dichloromethane. The organic phase is dried, concentrated and purified by chromatography over silica (eluant: cyclohexane/ethyl acetate 9/1) to yield the expected product.
Step 3: 5-Ethyl-1-fluoro-7H-cyclopenta[c]pyridine
A mixture of 1 g (4.87 mmol) of the compound described in the preceding Step and 200 mg (0.24 mmol) of ruthenium(IV) bis(tricyclohexylphosphine)benzylidene dichloride are dissolved in 20 ml of toluene. The solution is stirred at room temperature for 15 hours and then filtered. The filtrate is concentrated and purified by chromatography over silica (eluant: cyclohexane/ethyl acetate 8/2) to yield the expected product.
Step 4: (5S)-5-Ethyl-1-fluoro-6,7-dihydro-5H-cyclopenta[c]pyridine-5,6-diol
50 ml of distilled water, 9 g (27.3 mmol) of potassium ferricyanide, 3.6 g (28 mmol) of potassium carbonate, 10 mg (0.03 mmol) of potassium osmate dihydrate and 0.85 g (8.9 mmol) of methanesulphonamide are added, in succession, to a solution of 80 mg (0.01 mmol) of (DHQD)2-Pyr in 50 ml of tert-butyl alcohol After 3 minutes"" stirring at room temperature, the mixture is cooled to 0xc2x0 C. and a solution of 1.4 g (8.6 mmol) of the compound described in the preceding Step in 5 ml of tert-butyl alcohol is added. The reaction mixture is stirred for 2 days at 0xc2x0 C. The mixture is extracted with ethyl acetate, and the organic phases are dried, concentrated and purified by chromatography over silica (eluant: cyclohexane/ethyl acetate 5/5) to yield the expected product.
Step 5: (5S)-5-Ethyl-1-fluoro-5-hydroxy-5,7-dihydro-6H-cyclopenta[c]pyridin-6-one
0.82 ml of dimethyl sulphoxide is added, at xe2x88x9278xc2x0 C., to a mixture of 1.1 g (5.5 mmol) of the compound described in the preceding Step and 0.48 ml (5.5 mmol) of oxalyl chloride in 100 ml of dichloromethane. After 20 minutes at xe2x88x9278xc2x0 C., 4 ml (28.4 mmol) of triethylamine are added and the mixture is stirred for 15 minutes at low temperature, and returned to room temperature. The reaction mixture is hydrolysed with 100 ml of water and extracted with dichloromethane. The organic phase is washed with an aqueous 1% hydrochloric acid solution and then with an aqueous saturated sodium hydrogen carbonate solution. Drying and concentration yield the expected product.
Step 6: (5S)-5-Ethyl-5-hydroxy-5,7-1H-cyclopenta[c]pyridine-1,6-(2H)-dione
The expected product is obtained according to the process described in Step 4 of Preparation F using the compound described in the preceding Step as starting material.
Preparation J: 5-Ethyl-5-hydroxy-5,8-dihydro-1-(2H)-isoquinolinone
Step 1: 1-(3-Allyl-2-fluoro-4-pyridinyl)-1-propanol
The expected product is obtained according to the process described in Step 1 of Preparation I, replacing 3-pentanone by propanal.
Step 2: 1-(3-Allyl-2-fluoro-4-pyridinyl)-1-propanone
0.5 g of Celite, 0.2 g of 4 xc3x85 molecular sieve and 0.58 g (2.69 mmol) of pyridinium chlorochromate are added, at 0xc2x0 C., to a solution of 0.5 g (2.56 mmol) of the compound described in the preceding Step in 25 ml of dichloromethane. After returning to room temperature, the mixture is stirred for 15 hours and then filtered. The filtrate is concentrated and purified by chromatography over silica (eluant: dichloromethane/acetone, 97/3) to yield the expected product.
Step 3: 3-(3-Allyl-2-fluoro-4-pyridinyl)-1-penten-3-ol
2.1 ml of a 1 M solution of vinylmagnesium bromide in THF are added at 0xc2x0 C. to a solution of 0.32 g (1.66 mmol) of the compound described in the preceding Step in 10 ml of THF. After 45 minutes"" stirring at 0xc2x0 C., the mixture is hydrolysed with a 1M hydrochloric acid solution, and extracted with ether. The organic phases are washed with an aqueous saturated sodium hydrogen carbonate solution, dried over magnesium sulphate and concentrated. The residue is purified by chromatography over silica gel (eluant: dichloromethane/acetone, 95/5) to yield the expected product.
Step 4: 5-Ethyl-1-fluoro-5,8-dihydro-5-isoquinolinol
The expected product is obtained according to the process described in Step 3 of Preparation I, using the compound described in the preceding Step as starting material.
Step 5: 5-Ethyl-5-hydroxy-5,8-dihydro-1-(2H)-isoquinolinone
5 g (45 mmol) of potassium tert-butylate are added to a solution of 0.5 g (2.59 mmol) of the product described in the preceding Step in 25 ml of tert-butanol. After 16 hours"" stirring at reflux, the reaction mixture is cooled and hydrolysed with 50 ml of water and rendered acidic with a 2M hydrochloric acid solution. The resulting precipitate is filtered off and dried to yield the expected product.
Preparation K: 5-Ethyl-5-hydroxy-5,8-dihydro-1,6,7-(2H)-isoquinolinetrione
Step 1: 5-Ethyl-5,6,7-trihydroxy-5,6,7,8-tetrahydro-1-(2H)-isoquinolinone
4 ml of a 2.5% solution of osmium tetroxide in tert-butanol and then 1.5 g of N-methyl-morpholine N-oxide (12.8 mmol) are added at room temperature to a solution of 2 g (10.4 mmol) of the compound described in Preparation J in a mixture of 70 ml of dioxane and 30 ml of water. After stirring overnight at room temperature, the mixture is extracted with ethyl acetate, and the organic phases are dried and concentrated to yield the expected product.
Step 2: 5-Ethyl-5-hydroxy-5,8-dihydro-1,6,7-(2H)-isoquinolinetrione
1.30 ml of dimethyl sulphoxide (18.2 mmol) are added at xe2x88x9278xc2x0 C. to a mixture of 1 g (4.44 mmol) of the compound described in the preceding Step and 0.78 ml (8.88 mmol) of oxalyl chloride in 100 ml of dioxane. After 30 minutes at xe2x88x9278xc2x0 C., 6 ml (42.6 mmol) of triethylamine are added. After 15 minutes"" at xe2x88x9278xc2x0 C., the mixture is returned to room temperature. The reaction mixture is hydrolysed with 100 ml of water and extracted with ethyl acetate. The organic phase is washed with a 1N hydrochloric acid solution and then with an aqueous saturated sodium hydrogen carbonate solution. Drying and concentration yield the expected product.
Preparation L: 7-Ethyl-7-hydroxy-2,4,7,7a-tetrahydroxireno[2,3-g]isoquinolin-3(1aH)-one
1.17 g (6.8 mmol) of m-chloroperbenzoic acid are added at 0xc2x0 C. to a solution of 1 g (5.2 mmol) of the product described in Preparation J in 100 ml of dioxane. After stirring for 1 hour at room temperature, the solution is diluted with 100 ml of ethyl acetate and washed with an aqueous saturated sodium hydrogen carbonate solution. Drying over magnesium sulphate and removal of the solvents by evaporation yield the expected product.
Preparation M: 5-Ethyl-5-hydroxy-2,5,6,9-tetrahydro-1H-cyclohepta[c]pyridin-1-one
The expected product is obtained according to the process described in Preparation J, replacing vinylmagnesium bromide in Step 3 by allylmagnesium bromide.
Preparation N: 5-Ethyl-5-hydroxy-5,6,8,9-tetrahydro-1H-cyclohepta[c]-pyridine-1,7(2H)-dione
Step 1: (2-Fluoro-4-iodo-3-pyridinyl)methanol
0.72 g (19.2 mmol) of sodium borohydride is added to a solution of 4 g (16 mmol) of 2-fluoro-4-iodo-3-pyridinecarbaldehyde (described in J.O.C., 1993, 58, pp. 7832) in 100 ml of tetrahydrofuran. The mixture is stirred at room temperature for 4 hours and then hydrolysed. The reaction mixture is extracted with ethyl acetate. The organic phases are dried and concentrated to yield the expected product.
Step 2: 2-Fluoro-4-iodo-3-[(2-methoxyethoxy)methyl]pyridine
A solution of 2.1 g (16.8 mmol) of chloromethoxy-2-methoxyethane in 10 ml of dichloromethane, and then a solution of 2.2 g (16.8 mmol) of ethyldiisopropylamine and 180 mg (1.4 mmol) of 4-dimethylaminopyridine in 10 ml of dichloromethane are added, in succession, to a solution of 3.5 g (14 mmol) of the compound described in the preceding Step in 20 ml of dichloromethane. The mixture is stirred for 18 hours and then hydrolysed. The mixture is extracted with dichloromethane, and the organic phase is washed with an aqueous saturated sodium chloride solution until neutral, dried and concentrated to yield the expected product.
Step 3: 1-{2-Fluoro-3-[(2-methoxyethoxy)methyl]-4-pyridinyl}-1-propanol
The expected product is obtained according to the process described in Step 2 of Preparation G, using the compound described in the preceding Step as starting material and using propionaldehyde as electrophilic agent.
Step 4: 1-{2-Fluoro-3-[(2-methoxyethoxy)methyl]-4-pyridinyl}-1-propanone
The expected product is obtained according to the process described in Step 1 of Preparation E, using the compound described in the preceding Step as starting material.
Step 5: Methyl 3-{2-fluoro-3-[(2-methoxyethoxy)methyl]-4-pyridinyl}-3-hydroxypentanoate
A solution of 3 g (10.2 mmol) of the compound described in the preceding Step and 5.1 g (33 mmol) of methyl bromoacetate in 40 ml of THF is added dropwise to a suspension in 5 ml of THF, at reflux, of 2.16 g (33 mmol) of zinc, previously activated by treatment with 6M hydrochloric acid, in such a manner as to maintain reflux. Once the addition is complete, the mixture is stirred at reflux for 1 hour, and then cooled and hydrolysed with an aqueous saturated ammonium choride solution. After extraction with ether, the organic phase is dried, concentrated and purified by chromatography over silica (eluant: dichloromethane/acetone, 95/5) to yield the expected product.
Step 6: Methyl 3-[2-fluoro-3-(hydroxymethyl)-4-pyridinyl]-3-hydroxypentanoate
A solution of 3.5 g (10.1 mmol) of the compound prepared in the preceding Step in 20 ml of THF and 20 ml of 2N HCl is stirred at room temperature for 3 hours. The reaction mixture is decanted, the aqueous phase is extracted with ethyl acetate, the combined organic phases are washed until neutral with an aqueous saturated sodium chloride solution and dried over magnesium sulphate, and the expected product is obtained by removal of the solvents by evaporation.
Step 7: Methyl 3-(2-fluoro-3-formyl-4-pyridinyl)-3-hydroxypentanoate
1.2 g (13.9 mmol) of manganese dioxide are added to a solution of 3 g (11.6 mmol) of the compound described in the preceding Step in 50 ml of dichloromethane. After 2 hours"" stirring at room temperature, the reaction mixture is filtered over Celite, and the filtrate is concentrated to yield the expected product.
Step 8: Methyl 3-[4-(1-ethyl-1-hydroxy-3-methoxy-3-oxopropyl)-2-fluoro-3-pyridinyl]-2-acrylate
The expected product is obtained according to the process described in Step 6 of Preparation G, using the compound described in the preceding Step as starting material.
Step 9: Methyl 3-[2-fluoro-3-(3-methoxy-3-oxopropyl)-4-pyridinyl]-3-hydroxypentanoate
The expected product is obtained according to the process described in Step 7 of Preparation G, using the compound described in the preceding Step as starting material.
Step 10: Methyl 3-[2-fluoro-3-(3-methoxy-3-oxopropyl)-2-oxo-1,2-dihydro-4-pyridinyl]-3-trimethylsilyloxypentanoate
A solution of 2.7 ml (15 mmol) of trimethylsilyl triflate in 5 ml of methylene chloride is added dropwise at 0xc2x0 C. to a solution of 3.1 g (10 mmol) of the compound prepared in the preceding Step and 3 g (30 mmol) of triethylamine in 20 ml of methylene chloride. The reaction mixture is stirred for 2 hours at 0xc2x0 C., and then hydrolysed with 20 ml of water. The organic phase is decanted and dried over magnesium sulphate. The expected product is obtained by removing the solvents by evaporation.
Step 11: Methyl 5-ethyl-1-fluoro-7-oxo-5-trimethylsilanyloxy-6,7,8,9-tetrahydro-5H-cyclohepta[c]pyridine-8-carboxylate
The expected product is obtained according to the process described in Step 9 of Preparation G, using the compound described in the preceding Step as starting material.
Step 12: 5-Ethyl-5-hydroxy-5,6,8,9-tetrahydro-1H-cyclohepta[c]pyridine-1,7(2H)-dione
A suspension of 1.7 g (5 mmol) of the compound prepared in the preceding Step in 20 ml of a Normal solution of potassium hydroxide is heated at reflux for 2 hours. The reaction mixture is cooled to room temperature, rendered acidic by the addition of 40 ml of a 6N hydrochloric acid solution and stirred at room temperature for 30 minutes and then at 80xc2x0 C. for 1 hour. After cooling, the mixture is extracted with methylene chloride. The organic phase is dried over magnesium sulphate and concentrated to yield the expected compound.
Preparation O: 5-Ethyl-5-hydroxy-2,5,6,8-tetrahydro-1,7-isoquinolinedione
2 ml of boron trifluoride-diethyl ether complex (16.7 mmol) are added, at xe2x88x9278xc2x0 C., to a solution of 1 g (4.8 mmol) of the product described in Preparation L in 100 ml of dioxane. After returning to room temperature, the mixture is stirred for 20 hours, and then poured into a mixture of ethyl acetate/water. The organic phases are dried over magnesium sulphate. Removal of the solvents by evaporation yields the expected product.